My car reportedly has a 52.3 litre fuel tank capacity, yet when I completely fill my tank and drive until fuel light comes on, I have only used 40 ltrs?

Somebody says that the fuel gauge reading on all car's is wrong and just ignore it, that I still have more fuel. so what they are saying then is that when the fuel light comes on that I can drive for another 130 miles as I still have 13 litres of fuel left ? ?????

I can't believe that to be honest.

So why does it only take 40 litres to fill my tank from empty to full when the tank capacity is reported to be 52.3 ?

How the heck am I supposed to work out my MPG ?

To work out your MPG just fill the tank to the brim, reset the trip meter and drive it until it gets low, or at least low according to the gauge. Then refuel and see how many litres it takes to fill to the brim again (thus how many litres you have consumed).

You then convert the litres to gallons (1 gallon is around 5 litres) and divide the miles traveled by the gallons consumed.

As for the tank capacity, the only way to really check that would be to physically inspect the tank to see if it is original or not.

To be honest, why does it matter? Just fill it up when the gauge gets low.

My car reportedly has a 52.3 litre fuel tank capacity, yet when I completely fill my tank and drive until fuel light comes on, I have only used 40 ltrs?

Somebody says that the fuel gauge reading on all car's is wrong and just ignore it, that I still have more fuel. so what they are saying then is that when the fuel light comes on that I can drive for another 130 miles as I still have 13 litres of fuel left ? ?????

I can't believe that to be honest.

So why does it only take 40 litres to fill my tank from empty to full when the tank capacity is reported to be 52.3 ?

How the heck am I supposed to work out my MPG ?

Simple answer, the difference is the reserve :)

And as Jamie has said fill up to the brim the same each time, then the amount of fuel you put in is what you have used since your last fill up. So just note the mileage at every fill up. I use an app on my phone to note it and work it out automatically.

Simple answer, the difference is the reserve :)

And as Jamie has said fill up to the brim the same each time, then the amount of fuel you put in is what you have used since your last fill up. So just note the mileage at every fill up. I use an app on my phone to note it and work it out automatically.

Yes, that's the one thing I forgot to say! The calculator tool I use is: http://www.mpg-calculator.co.uk/

As Alex suggested, an app on your phone is the best way to work out your mpg. Just make sure you always fill to the brim so you will know exactly how much fuel you used, then you just need to record the distance travelled and keep the receipt with the amount of fuel used.

The app I use is "My Cars" which makes all this very easy and gives you all sorts of data and graphs to look at (most importantly tells me exactly what my monthly fuel cost is). I always reset everything on my trip computer when I fill up, after recording all of it in the app. Then fill in the fuel amount later so you're not sat there holding people up lol.